Grhl3 and Lmo4 play coordinate roles in epidermal migration

Area of Science:

• Developmental biology
• Molecular biology
• Genetics

Background:

• Grainy head-like 3 (Grhl3) is crucial for epidermal barrier formation, neural tube closure, and wound repair, processes involving epidermal migration.
• The precise molecular mechanisms and interacting partners of Grhl3 in these processes are not fully understood.

Purpose of the Study:

• To investigate the functional partnership between Grhl3 and LIM-only domain protein 4 (LMO4).
• To define a novel cooperative role for Grhl3 and LMO4 in developmental epidermal migration, specifically eyelid fusion.

Main Methods:

• Biochemical and genetic interaction studies in mice.
• Analysis of mutant mice with combined Grhl3 and LMO4 deficiencies.
• Electron microscopy of embryonic tissues.
• In vitro keratinocyte scratch assays.

Main Results:

• Grhl3 and LMO4 interact biochemically and genetically.
• Combined Grhl3/LMO4 deficiency leads to severe developmental defects, including exencephaly, spina bifida, defective skin barrier, and a fully penetrant eyes-open-at-birth phenotype.
• Mutant embryos exhibit impaired eyelid fusion due to failed epithelial extension and lack of peridermal clump formation.
• Loss of Grhl3/LMO4 disrupts actin fiber accumulation and ERK1/2 phosphorylation in migrating epidermis.
• Mutant keratinocytes show impaired wound healing in vitro, indicating a general epidermal migratory defect.

Conclusions:

• LMO4 is a functional partner of Grhl3 in epidermal barrier formation, neural tube closure, and wound repair.
• Grhl3 and LMO4 cooperate in the developmental process of eyelid fusion.
• The Grhl3-LMO4 complex regulates epidermal migration through ERK activation and actin cable formation.